.el {
  width: 200px;
  height: 200px;
  border: 6px solid black;
  border-radius: 24px;
  background: conic-gradient(
    from 0.25turn at 0 0,
    green 0 45deg,
    white 45deg 
  );
}
body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
}